1. Field of the Invention
The present invention relates to a liquid crystal display device and a manufacturing method thereof.
2. Description of the Related Art
As a display device which is thin and lightweight (a so-called flat panel display), a liquid crystal display device including a liquid crystal element, a light-emitting device including a self-luminous element, a field-emission display (an FED), and the like have been competitively developed.
Since many optical members such as a polarizing plate and a backlight are used in a liquid crystal display device widely used as a display device, material cost or power consumption of the backlight needs to be reduced.
In addition, a liquid crystal display device has various modes, and a TN mode using a nematic liquid crystal in the twist alignment or an STN mode using a nematic liquid crystal in the supertwist alignment is mainly used. However, a pair of polarizing plates is required by the operating principle of these modes, and thus transmittance is low and bright display cannot be obtained due to the light absorption by the polarizing plates.
Further, other than these modes, a guest-host liquid crystal using a dichroic pigment has been developed. In a display device using a guest-host liquid crystal, dichroic pigments are mixed as guest molecules with host molecules in a liquid crystal layer, and each alignment of the host molecule and the guest molecule is changed by voltage applied to the liquid crystal, so that the light absorptance of the liquid crystal layer is changed. A rod-like dichroic pigment has a property of being oriented in parallel with the host molecule, when the dichroic pigment is used as a guest molecule. Accordingly, for example when the alignment of the host molecule is changed by applying voltage, the alignment of the dichroic pigment is concomitantly changed.
In addition, a reflective liquid crystal display device in which the guest-host liquid crystal and a reflective film, or the guest-host liquid crystal and a reflective plate, are combined has been developed. In the reflective liquid crystal display device, images can be displayed without using a backlight source (a backlight) and can be displayed only with external light, so that low power consumption can be achieved. In addition, since the reflective liquid crystal display device can be widely used for a display of a mobile information terminal and the like, and it has been researched for practical use.
One of the main components of the reflective liquid crystal display device using the guest-host liquid crystal is a reflective film or a reflective plate for reflecting light.
A conventional reflective film reflects incident light by specular reflection, so that when a panel is observed from the front, vertical incident light is reflected to the viewer side as vertical reflective light, whereby favorable display can be obtained. However, when the panel is observed from an oblique angle, incident light is hardly reflected to the viewer side, so that display visibility dropped. Further, when the reflecting surface is specular, the reflected image is seen in the display background, so that the display is hard to see.
As a measure against the problems, a reflective film having uneven shape in accordance with uneven shape which is made in a surface of a resin layer has been proposed (see Patent Document 1, for example). Accordingly, light incident from outside is scattered by using the reflective film, and a high reflecting property and display with high brightness can be realized.